iPhone 3G: 5 Days and Counting Down to GPS!

This is it. We're in the home stretch. Third period power play, clock's all but run out, and Steve Jobs is cranking back for the slap shot. In 5 days we find out if Apple scores the go-ahead goal, the two-peat for smartphone (even gadget) of the year, or if they bounce it off the goal post with their mostly evolutionary, not so much revolutionary, next generation handset.

What is this and why should it matter to you? Read on after the break!

The original iPhone (now dubbed iPhone 2G) launched without any location aware services. While it might or might not have known where it was, it didn't share that information with you. When firmware 1.1.3 was released, however, that all changed.

Using Google's cell tower mapping (where Google is recording the GPS positions of cell phone towers -- AT&T, Verizon, Bell, etc. in North America and increasingly around the world), and Skyhook's WiFi router mapping (where Skyhook drove down your street and wrote down the position and unique ID of your wireless router), this let the Google Maps app in the iPhone 2G kinda-sorta get a fuzzy idea of where it was. Drawbacks? It was about as precise as a few city blocks, and if for example, you were in New York but the closest router had just been shipped there from LA, you'd just as likely show up as being in the router's last-recorded location, LA. In other words it ranged from good enough to potentially equal parts comical or disastrous. Also, since transmitting the map graphics required an EDGE connection, it wasn't exactly speedy.

With the iPhone 3G, location becomes as precise as a few feet. Using an array of some three dozen satellites constantly beaming their signals down to us, the iPhone 3G trilaterates (i.e. figures out) exactly where we are based on which satellite's signals it receives and the distance of each of those signals. (Typically four or more signals are required, as unlike triangulation, it needs to calculate the timing of the signals as well). Geeky much? There's more.

GPS isn't all roses. It can often take considerable time and can burn a lot of power. It's another radio to leave running, and depending on signal strength, it can take minutes -- sometimes a lot of them -- to acquire satellites. Then its got to spend more time and power to crunch all the numbers.

To help compensate for this, the iPhone 3G uses aGPS (assisted GPS). With aGPS, cell phone towers handle acquiring the satellite signals and pre-crunch down the location information. Since cell phone towers, unlike tiny handsets, can host very large radios and much more computational power, they can receive more and better signals and they can keep track of location much faster. This means, when your iPhone 3G GPS goes active, a lot of the heavy lifting has already been done by the nearby cell towers, and it can just fetch the data and do the final, specific to its own location, calculations. This consumes less power and requires much less overhead than the iPhone 3G having to do all the work itself.

Speaking of consuming less power, the iPhone (and Apps via the SDK), is also able to leverage all three of its location-based technologies in an elegant, escalating manner, using only what it needs and only when it needs it. If you only require location within a few blocks, cell and wifi are enough and there's no need to waste power spinning up the GPS. Need something spot on? GPS is there, passed on the information, and then powers down again when it's no longer needed.